Wafers, such as those used in the manufacture of integrated circuits and similar technologies, are manufactured by highly complicated manufacturing processes. These manufacturing processes should be monitored in order to ensure the quality of the wafers.
The monitoring process may include a first phase of optical inspection, ultraviolet inspection, deep ultraviolet inspection or extreme ultraviolet inspection to detect potential defects and a second phase of defect review.
Defect review is usually executed by a scanning electron microscope that exhibits very high resolution (nanometric order) but is very slow.
A wafer is supported by a heavy mechanical stage. The heavy mechanical stage can weigh few hundred kilograms.
For each suspected defect the defect review process includes (a) mechanically moving the wafer (by the heavy mechanical stage) until the scanning electron microscope can view a suspected defect, (b) stopping the movement of the heavy mechanical stage, and (c) scanning the suspected defect while the wafer is stationary.
FIG. 1 illustrates wafer 10. Wafer 10 includes various suspected defects (denoted “o” 20, 201, 202 and 203). FIG. 1 also illustrates (dashed lines 30, 301, 302, 303) a scan pattern that is followed by the heavy mechanical stage. The heavy mechanical stage accelerated towards a suspected defect, decelerates until being stationary when reaching the vicinity of the suspected defect, and then waiting until the optics obtains an image of the suspected defect.
A review of about 100000 suspected defects of a 300 mm wafer can take a day—mostly because of the time required to accelerate the heavy mechanical stage and to decelerate the heavy mechanical stage until the heavy mechanical stage is stationary.
There is a growing need to accelerate the defect review process of suspected defects.